1. Field of the Disclosure
This disclosure relates to rock dusting compositions and methods of use thereof. The compositions are composed of rock dust, e.g., limestone or other mineral dust, water, pumping aid, and polymer, e.g., acrylamide homopolymers, acrylamide copolymers, and combinations thereof, and are applied to the surface of a mine. The compositions are useful for suppressing propagation of a flame and/or fire caused by ignition of coal dust and/or gas within a coal mine.
2. Discussion of the Background Art
It is well known that fires and explosions are a major hazard in the field of underground mining. The danger of fire and explosion is particularly acute in coal mining because of the existence of inherently explosive and flammable materials, such as methane gas and coal dust, in the underground coal mine.
The cause of such fires and explosions can be readily appreciated. Combustible materials are generally associated with the mining of materials, such as coal, which are based on organic chemicals. Not only is the coal itself combustible, but the mining operation produces small fragments of coal and coal dust which are introduced into the air. This material may well be combustible and even explosive under appropriate conditions.
Hydrocarbon gases are found in association with coal mine operations. The most commonly found gas is methane gas, the major component of natural gas. Other similar combustible hydrocarbon gases are also found in lesser quantities in association with coal mines. The gaseous materials which are released during coal mine operations are themselves extremely hazardous.
Coal mine operations can often result in sufficient sparks to ignite combustible and explosive materials. Coal mine operations require the use of many types of electrical apparatus as well as other types of machinery which can potentially produce sparks. The combination of spark-producing machinery and electrical equipment, and the extremely explosive and combustible coal dust and related gases, produces a hazardous situation.
The combination of potentially spark producing equipment and extremely combustible material found within underground mines has resulted in disaster on many occasions. In addition, underground explosions and fires are particularly difficult to survive. For example, the explosion may cause collapse of part of the mine tunnel. Fire and explosion underground produces large quantities of noxious gases which can easily produce personal injury or death to underground miners and others working underground. Thus, it can be seen that fires and explosions in underground mine operations are of particular concern to all involved.
Various solutions have been attempted in order to prevent fire and explosion in underground mine operations. A conventional method of minimizing the potential for fire and explosion has been to spread inert material within the interior of the mine. In some cases it is desirable to totally coat the interior walls, ceiling and floor of the mine tunnels. Adding inert material to the environment helps to maintain the ambient atmosphere within the mine at conditions which are not explosive or combustible. The inert materials spread onto the interior walls of the mine sufficiently dilute the mine dust and methane within the mine such that the atmosphere is not capable of propagating an explosion or fire. The coating also helps prevent further coal dust and the like from escaping into the air within the mine tunnel.
Dusting as a method of preventing explosions and fires within a mine has become accepted in the art. Under regulations promulgated pursuant to the Federal Coal Mine Health and Safety Act, dusting is now a requirement in many mines.
Regulations of the Mine Safety and Health Administration (“MSHA”) provide that the interior of coal mines and the like should be coated with a coating of rock dust. MSHA sets forth regulations concerning the use and spreading of rock dust.
Extensive governmental regulations governing the use and administration of rock dust are now in place. The situations in which rock dust is required are also defined in detail by specific regulation. Thus, mine operators now find themselves in the position of being required to comply with extensive regulation regarding rock dusting. Rock dusting within coal mines, therefore, is often no longer just one alternative to dealing with potentially hazardous conditions, but rather, is absolutely required in many settings.
As indicated above, in underground coal mines, stone dusting of exposed rock surfaces is used to prevent and suppress fires caused by the ignition of coal dust and methane gas produced during the mining process. Stone dusting involves coating the surfaces of the mine with a fine-ground limestone dust. The dust adheres to the walls of the mine and prevents propagation of fires along exposed surfaces of unmined coal in the mine. In the event of the ignition of coal dust and gas within the mine, the concussion of an explosion and fire will cause the loosely adhering dust to fall from the surfaces of the mine to produce a limestone dust-air suspension that suppresses the propagation of flame and stops the fire.
Applying rock dust to mine walls is usually accomplished by dry spraying. This method has draw backs since to get the required quantity of dust to adhere to the mine walls, substantial amounts of dust can become air born. To reduce the air born concentration water is added to the dusting compound, however the water requirements to maintain a pumpable mixture results in a substantial proportion of the product sloughing to the mine floor. Adhesives can be added to the wet mixed material to increase viscosity, however as the product dries it will cake to the mine walls, preventing adequate dispersion in a methane explosion.
There is a need in the art for rock dust compositions that can be applied to mine surfaces, e.g., walls, ceilings and floors, in which air borne particles are minimized or eliminated during application. There is also a need in the art for rock dust compositions that, in blast/concussion situations, will disperse from the mine surfaces as a powdered material, not as lumps or chunks, thereby suppressing any explosion that may occur from methane ignition.
The present disclosure provides many advantages, which shall become apparent as described below.